1. Field of the Invention
The invention relates to a valve assembly, more particularly to a discharge valve assembly having a metal intermediate ring formed with a valve hole so as to slowly and steadily discharge an air flow.
2. Description of the Related Art
For a variety of instruments that require slow and steady release of air pressure, such as a sphygmomanometer used for measuring blood pressure, a crucial factor to determine whether a measured value of blood pressure is accurate or not is the air discharge stability of a discharge valve assembly included in the sphygmomanometer. Referring to FIG. 1, a conventional discharge valve assembly disclosed in Taiwanese Utility Model No. M255707 includes a valve body 11, an elastic silicone air receptacle 12 that is inserted into the valve body 11 and that has a peripheral surface formed with a hole 120 that communicates with an inner side of the valve body 11, and an adjusting rod 13 that is inserted into the air receptacle 12. The adjusting rod 13 is movable relative to the air receptacle 12 so as to deform the air receptacle 12 to control an opening size of the hole 120, thereby adjusting the flow rate of air discharged therefrom.
For adjusting the flow rate of the discharged air based on the deformation adjustment of the hole 120 of the air receptacle 12, this kind of structural design has drawbacks related to an unstable flow rate of the discharged air due to elastic fatigue of the air receptacle 12 or difficulty in accurately and stably controlling the opening size of the hole 120 attributed to storage and/or transport temperature.